One objective in the design of semiconductor luminous elements is improved efficiency of light emission. An example of a semiconductor luminous element of the prior art which was designed for improved efficiency is disclosed in Japanese Patent Publication(Kokai Kohou 60-98689).
The configuration of this prior art semiconductor luminous element (or light emitting diode) is shown in FIG. 10. Semiconductor luminous element 90 consists of AlGaAs semiconductor substrate 91 and multilayer reflective film 92, GaAs active layer 93, and AlGaAs cladding layer 94, which are laminated atop substrate 91. Multilayer reflective film 92 consists of two types of semiconductor thin films, 92a and 92b, which are grown as crystals alternately until the laminate has at least twelve layers. On the upper surface of cladding layer 94 is insulation layer 95, consisting of SiO.sub.2 or some similar substance. On top of the insulation layer is A1 electrode 96. A window, 97, is provided in electrode 96 for the emission of light. On the periphery of window 97, electrode 96 comes in contact with cladding layer 94. An electrode 98 is formed on the lower surface of semiconductor substrate 91.
When the current is conducted from electrode 96 to active layer 93 in the region around the edges of window 97, light is emitted in the region of active layer 93 traversed by the current. The light projected upward by active layer 93 is channeled to the exterior via window 97. The light projected downward by active layer 93 is reflected by multilayer reflective film 92 and then channeled to the exterior via window 97.
The aforesaid semiconductor luminous element 90 has a multilayer reflective film 92 sandwiched between semiconductor substrate 91 and active layer 93. Thus the light emitted by active layer 93 which proceeds in the direction of semiconductor substrate 91 can be reflected by multilayer film 92 and channeled toward window 97 so as to increase the efficiency of emission.
However, a semiconductor luminous element 90 with the configuration described above channels to the exterior only the light reflected toward window 97 on the first reflection. Since the light-emitting region of luminous element 90 is microscopic, the efficiency of emission can only be improved slightly. If we wish further to improve the efficiency, this design does not seem promising.